It is well known that cereal aggregates are normally required to have suitable organoleptic characteristics such as friability, crispness, an ability to absorb liquids, as well as having a pleasing shape and being easy to work by machine or to handle, that is, being able to withstand all of the mechanical operations provided for after their moulding, for example, such as packaging, without crumbling or requiring the use of special and complex machines or devices for these operations.
Essentially, the production of products of the aforementioned type (cereal aggregates) on an industrial scale provides for the selected cereals to be cooked in water, generally until the starch which they contain has fully gelled, and then to be divided into pieces or pellets which are subjected to a mechanical flaking operation producing the well-known so-called cereal flakes.
Predetermined quantities of cereal flakes are then metered into suitable moulds of predetermined shape and size in which the cereal flakes are compacted producing moist cereal aggregates which are finally dried to produce to the desired biscuits. The cereal flakes are normally compacted with the use of mechanically or hydraulically-operated pressure elements which cooperate with the moulds.
The compacting pressure is selected according to the apparent density and the consistency to be attributed to the finished product (the aggregate).
It is quite gentle when the product is to be particularly light, that is, when a large number and high density of air pockets are to be formed between the cereal flakes constituting it; it must be quite high, however (for example, to reduce the initial volume of the flakes loaded into the respective moulds by half) when a product as free as possible of air trapped between the cereal flakes (an aggregate with a "high" apparent density) is to be produced.
In the former case, to ensure as far as possible that the aggregate can be handled from the moment when it is released from the mould, that is, to combat its tendency to crumble and disintegrate, the cereal flakes have to have a moisture content of 23-30% and have to be mixed with a binding "system" constituted by sugars and fats (of either animal or vegetable origin) in quantities such that fats represent at least 18-25% of the final product.
In the latter case, the flakes must have a moisture content of 6-10% and a reduced quantity of binder to prevent excessive hardness of the finished product.
The present invention relates to a method and equipment for continuously producing cereal aggregates of the second type mentioned above on an industrial scale.
As already mentioned, in order to produce cereal aggregates of relatively "high density", the prior art provides for compacting machines which comprise essentially a cup- or beaker-shaped mould supported in a fixed vertical position, and a piston movable in the mould and constituting the base thereof, the piston cooperating with a mechanically-operated pressure element.
The piston (or movable base) can be positioned in the mould in various ways to define the required quantity of cereals to be compacted; moreover, upon completion of the compacting, it can be used to expel the cereal aggregate produced from the mould.
A first recognized disadvantage of compacting machines of the aforementioned type is that they are wholly inadequate for production on an industrial scale because they operate decidedly intermittently, and also on account of the mechanically imposed limit on the number of "strokes" per minute which the punch-piston pair can carry out without compromising the operation of the machine. In fact, it must be born in mind that, inside the moulds the greater stresses due to the compression stage are withstood by the movable bases and by the lever systems and mechanisms associated therewith.
Another disadvantage is connected with the fact that these compacting machines always require the manual intervention of several operators and/or of special and complex devices for loading the moist cereal aggregates just released from the moulds in an orderly manner onto the conveyor belts of the large tunnel drying ovens normally used in the food industry.
Another disadvantage is connected with the so-called "elastic memory" generally possessed by the quantity or mass of cereal flakes to be compacted; that is, the tendency for the mass to go back to its original volume when the compacting pressure thereon ceases. This "elastic memory" which is due essentially to the intrinsic resilience of the cereal flakes and to the presence of a greater or lesser density of air pockets between them, results in the already-mentioned tendency of the cereal aggregates just produced to crumble.
This tendency is present in most of the cereal aggregates produced by the methods and by the compacting machines of the prior art, even when the compacting pressure is high and/or is maintained for prolonged periods. High compacting pressures give products which are not optimal from an organoleptic point of view, whereas prolonged compacting times adversely affect the productivity of the machines which is already quite poor.